Flowable material is typically removed from pressurized and vacuumized chambers with dual valve systems as such systems allow material to be removed from the chamber without a substantial loss in the pressure or vacuum. Typical dual valve systems comprise a pair of longitudinally aligned, cooperatively operational disk valves which sealingly contact the inner wall of the surrounding conduit when closed. The disk valves define a transition chamber therebetween.
Material is conveyed through dual valve systems by closing the bottom-most valve, opening the top-most valve so as to allow material to flow into the transition chamber, closing the top-most valve, and opening the bottom-most valve so as to allow the material in the transition chamber to flow out of the system.
Unfortunately, the valve to conduit contact points in typical dual valve systems tend to quickly wear to the point where a tight seal is no longer possible and repair is necessary. To repair the typical dual valve system it is necessary to replace the valves and either replace and/or rebore the conduit; a difficult, time consuming and costly job.
Accordingly, a need exists for a dual valve system which may be quickly, easily and inexpensively repaired.